The technological background of the invention assumes a knowledge of prior data that can be found in reference documents forming part of the general knowledge of the person skilled in the art, in particular the documents listed below:
Title of thedocumentReference of the document or contentDVB MultimediaDVB MHP TAM232 r16Home PlatformHypertext TransferRFC 2616 HTTP 1.1Protocol (HTTP)http://www.w3.org/Protocols/rfc2616/rfc2616.htmlUniform ResourceRFC 2396 http://www.ietf.org/rfc/rfc2396.txtIdentifier (URI)HTMLHTML 4.01 Specificationspecificationhttp://www.w3.org/MarkUp/The ExtensibleXHTML ™ 1.0: The Extensible HyperText MarkupHyperText MarkupLanguage A Reformulation of HTML 4 in XML 1.0Languagehttp://www.w3.org/TR/xhtml1/Extensible MarkupXML - W3C recommendationLanguagehttp://www.w3.org/TR/1998/rec-xml-19980210
The description of the state of the art and of the invention also assumes that abbreviations commonly employed by the person skilled in the art are known. It is so common to employ these abbreviations that the person skilled in the art understands better what is being explained to him when these abbreviations are employed than when complete expressions are employed. A list of these abbreviations corresponding generally to initials in English is given below.
DSM-CC(Data Storage Media Command and Control)DVB(Digital Video Broadcasting)XLETApplication package objects allowing the execution of JAVAapplets that may have access to resources of a decoder[DVB-MHP; DVB-HTML]HTML(HyperText Markup Language) Language allowing thedesignation of links between textsHTTP(HyperText Transfer Protocol) protocol for transferringtexts in which links to other texts are definedMMIMan Machine InterfaceMIME(Multipurpose Internet Mail Extensions) Extension makingit possible in particular to ascertain the definition ofthe content of a fileMHPMultimedia Home PlatformMPEGMoving Picture Experts GroupOCGObject Carousel GeneratorSSLSocket Secure LayerTLSTransport Layer SecurityURIUniform Resource Identifier of character allowing theidentification of a resourceURLUniform Resource Locator, locating of a document throughits protocol, machine, directory, name of the documentWWWWorld Wide WebXHTMLThe Extensible HyperText Markup Language
Finally, a few terms used in the present document should be made precise:
Subscriber orUser of an HTML application executing theend userapplication with the aid of a navigatorintegrated into a digital decoderApplicationHTML application: the whole set of pages andtree structure of the siteDocument orAny file accessible on a remote http serverfilethrough a URLHome documentComplete URL determining the site entry pointIncluded documentDocument included in a main page: picture, sound,or includedsecondary document, application. An includedcomponentdocument will be inserted into the page withoutany intervention by virtue of instructions of aprogram for presenting the page containing inparticular the URL of the included document andtags for locating the included document in thepage involved.Document or fileDocument accessible from a main page by clickinglinked oron a hyperlinkpointed atMain documentDocument or file accessible by clicking on aor filehyperlink and which is not included in any otherdocumentDynamismThe dynamism of a document makes it possible toadvise the OCG of documents liable to requiremore frequent updatingPageMain documentPriorityThe priority of a document determines itsfrequency of transmission. Thus, a document ofhigh priority will be transmitted more frequentlythan a document of low priorityProxyServer acting as gateway to the InternetSiteSet of pages served by the WEB server CompleteURL of a home page, associated with site limitdefinition and depth parameters
Typically an application is made up of a plurality of HTML pages, known as interactive pages.
To download an application, use is made of TCP/IP protocols such as HTTP (hyper text transfer protocol). The application is forwarded from an HTTP server, to a server for transmitting applications (Broadcast Application Servers—BAS) in the form of a tree of files and is then encapsulated into modules, each containing one or more files, in a carousel object transfer protocol such as “Object Carousel Protocol” and inserted into an MPEG stream transmitted for example by a satellite or by cable.
According to the prior technique, a protocol such as DSM-CC Object Carousel complies with the tree structure of the application. The transmission by means of such a protocol complies with the properties of the file system (directory tree) and allows the encapsulation in MPEG sections.
The tree of the application is a directory tree, these directories containing the various files of the application. Thus, for example, it will be possible to have a root directory to which a 0 level is given to which are attached files of level 0 and directories of level 1. The directories of level 1 contain files of level 1 and directories of level 2 and so on and so forth. In general the directories are organized by type of content, for example a directory of images will contain all the images of the application, the corresponding files have a “.gif” termination, another directory will contain the sound products, etc.
This protocol according to the prior technique is suitable for the transmission of a tree of file management systems, but is of no help whatsoever in optimizing the transmission as soon as dependencies, in the form of navigation links, also called hyperlinks, appear between these files, this being the case for an HTML application. Moreover, included components (applet images, sound, etc., this list not being limiting) pointed at by an inclusion link in an HTML file (or main file), necessary for the formulation of the interactive page are not transmitted in an optimal manner in a mode that takes account only of the file tree. Specifically, the page will actually be made available to the end user only after a time corresponding to one or more transmission cycles, if certain included components necessary for the displaying of a page are located in a directory that is very far away from the root directory. Thus from the user's point of view the page access time may be very long and discourage access. The reconstruction of a main document will only be possible when all the included files, for example images or sounds, have been received.